Conventionally, silicone rubbers are superior in heat resistance, cold resistance, and weather resistance, therefore they are being utilized in various fields. However, low molecular weight siloxanes are undesirable for parts which are exposed to electrical contact or that are utilized in the vicinity thereof, or for the parts of office automation (OA) instruments such as copiers, facsimile machines and personal computers, particularly such as for roll materials in a copying machine. Therefore silicone rubbers for these purposes are desired to have a reduced content of low molecular weight siloxanes. This is because the low molecular weight siloxanes in silicone rubber tend to cause troubles such as improper contact and unclear images.
The conventional countermeasures for this problem are: the utilization of an organopolysiloxane, from which the low molecular weight siloxane components have been removed by reduced pressure stripping, as a base component of the silicone rubber, and the application of a long post-curing process to the cured silicone rubber in order to volatilize the low molecular weight siloxanes from the cured product.
However, the following problems are still noticed. The reduced pressure stripping may easily remove the low molecular weight siloxane components existing in the organopolysiloxane which have a low degree of polymerization, but does not remove the components existing in the organopolysiloxane with a relatively high degree of polymerization. In addition, the application of a long post-cure process is extremely disadvantageous from the industrial view point. Therefore, neither method is a conclusive solution.
Further, addition of a large amount of sellaite powder, reinforcing filler, or spherical silica powder may relatively reduce the content of the low molecular weight siloxane components. In this case, however, the rubber hardness increases and other critical disadvantages occur, such as a loss of the rubber elasticity characteristic of the silicone rubber, and a loss of heat resistance and weather resistance.
Therefore, an object of this invention is to provide a silicone rubber roll wherein the content of the low molecular weight siloxanes is suppressed.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.